World Spay Day

World Spay Day, held annually on the last Tuesday of February, is a global campaign by Humane Society International to promote neutering of companion animals and feral cats as the most effective tool for reducing overpopulation and improving animal welfare.

DateLast Tuesday of February (2027: 23 Feb)

Organised byHumane Society International (HSI)

FocusSpay/neuter access and awareness worldwide

FormatOnline campaigns, discounted neutering clinics (varies by region)

Why neutering matters for cats

A single unspayed female cat can, in theory, be responsible for thousands of offspring over her lifetime — through her own kittens and their descendants. Shelter overcrowding, euthanasia of healthy cats, and the welfare challenges of large feral colonies are all downstream consequences of uncontrolled reproduction.

Neutering is the most cost-effective single intervention for reducing cat overpopulation. It is also directly beneficial for the individual cat's health — particularly for females, where the benefits are most pronounced.

Health benefits by sex

Female (spaying)

Prevents pyometra — life-threatening uterine infection affecting ~25% of unspayed cats by age 10
Greatly reduces mammary tumour risk — especially when done before first season
Eliminates ovarian and uterine cancer
Prevents the stress and physical cost of repeated pregnancies and seasons
Reduces roaming (and associated road traffic risk)

Male (castration)

Eliminates testicular cancer
Reduces urine spraying in most cats (particularly if done before spraying begins)
Reduces roaming, fighting, and bite wounds — and therefore FIV/FeLV transmission risk
Reduces inter-cat aggression in multi-cat households
Generally calmer, more home-oriented behaviour

The evidence base for these benefits is summarised in the Merck Veterinary Manual reproductive management chapter and endorsed by International Cat Care.

Timing matters for females. Spaying before the first season reduces mammary tumour risk by approximately 91%. After the first season, the reduction is around 86%. After the second season, the protective effect drops to 11%. Spaying early is significantly better than spaying late, even if late spaying is still worthwhile.

How to get involved on World Spay Day

Book your cat's neutering appointment if it has not been done yet
Donate to a local rescue running a neutering assistance programme
Share verified information about neutering benefits — particularly the mammary tumour statistics, which are not widely known
In the US, HSI's World Spay Day page lists participating clinics offering discounted procedures

Frequently asked questions

What is World Spay Day?

World Spay Day is an annual campaign held on the last Tuesday of February, organised by Humane Society International (HSI). It promotes spaying and neutering of companion animals and stray/feral cats worldwide to reduce overpopulation, disease, and shelter overcrowding.

At what age should a cat be neutered?

The International Cat Care guidance on neutering and the AAHA recommend neutering cats from around four months of age — before the first season for females. Early neutering (before the first season) significantly reduces the risk of mammary tumours. Your vet will advise on the timing most appropriate for your cat.

What are the health benefits of neutering a cat?

For females: elimination of pyometra risk (life-threatening uterine infection), near-elimination of mammary tumour risk if done before first season, prevention of unwanted pregnancy. For males: elimination of testicular cancer, reduction in roaming and fighting (which reduces road traffic injury and infectious disease transmission). Both: reduction in spraying, lower risk of FIV and FeLV transmission through bite wounds. Summary in Merck Veterinary Manual.

Does neutering change a cat's personality?

Neutering reduces hormonally driven behaviours — roaming, spraying, yowling in season, aggression over territory — but does not change a cat's fundamental character. A playful cat remains playful; an affectionate cat remains affectionate. The reduction in testosterone or oestrogen removes behaviours that are stressful for the cat, not enriching ones.

Are there any risks to neutering?

Neutering is one of the most commonly performed surgical procedures in veterinary medicine. Serious complications are rare. There is a small increase in risk of urinary issues in male cats if neutered very early (before 12 weeks), and neutered cats have a somewhat higher risk of obesity — manageable with appropriate diet and exercise. The benefits substantially outweigh the risks for the vast majority of cats.